Visual QCD Archive

The QCD Vacuum

Here you'll find images and animations of the quantum fluctuations of
the vacuum of QuantumChromodynamics (QCD). These images have been
created via supercomputer simulations of QCD on a
243 × 36 space-time lattice using a
128-node Thinking Machines CM5.

Acknowledgments

My thanks to John Ahern, Frederic Bonnet, Sundance Bilson-Thompson,
Patrick Fitzhenry, Greg Kilcup, Mark Stanford and Tony Williams for
their contributions to making these images possible. Additional
thanks to Francis Vaughan of the SACPC for
generous supercomputer support and the DHPC Group for support in
the development of parallel algorithms.

To eliminate the short range perturbative fluctuations and reveal
the interesting long-distance non-perturbative phenomena, the
fields are "cooled" by an algorithm which smoothes the fields
locally by considering nearest neighbor interactions.

Topological charge is a measure of the winding in the gluon field
configuration. After seven sweeps of cooling, lumps in the
topological charge density appear. The topological charge
density can be positive (red) or negative (blue).

Instantons are four dimensional objects. This animation
illustrates the fourth dimension by stepping through the fourth
dimension of the periodic lattice. This is a good animation for
seeing and understanding the structure of these 4 dimensional
objects.

This animation illustrates the fourth dimension of instantons by
stepping through the fourth dimension of the periodic lattice.
This is also a good animation for seeing and understanding the
topological structure of these 4 dimensional objects.

This animation and the following feature another instanton
anti-instanton annihilation. This time we are watching the same
field configuration but at a different time slice. Watch the
upper-centre of the lattice.

The first 30 frames illustrate cooling with the 5-loop
over-improved action of de Forcrand et al. The 31st frame
shows the result of 30 sweeps of cooling with the standard 1-loop
action. The remainder of the animation shows 1-loop cooling in
reverse. The gauge field is from an order-a2
improved action on a 163 × 32 space-time
lattice.

This animation illustrates the behavior of the topological charge
density obtained from a three-loop improved definition of the
field strength tensor (which has smaller
O(a6) errors than four or five loop
improved operators). Cooling proceeds via a five-loop improved
estimate of the action. Instanton anti-instanton interactions
are featured in the lower right-hand corner of the animation.

This animation illustrates the fourth dimension of a highly
cooled configuration with Q=-2 and S/S0=3.7. The
topological charge density is obtained from a three-loop improved
definition of the field strength tensor (which has smaller
O(a6) errors than four or five loop
improved operators). Cooling proceeds via a three-loop improved
estimate of the action.

Three quarks indicated by red, green and blue spheres (lower
left) are localized by the gluon field.

A quark-antiquark pair created from the gluon field is
illustrated by the green-antigreen (magenta) quark pair on the right.
These quark pairs give rise to a meson cloud around the
proton.

The masses of the quarks illustrated in this diagram account for
only 3% of the proton mass. The gluon field is responsible for the
remaining 97% of the proton's mass and is the origin of mass in most
everything around us.

Experimentalists probe the structure of the proton by scattering
electrons (white line) off quarks which interact by exchanging a
quantum of light (wavy line) known as a photon.